The present invention relates to a closure cover to be fastened, preferably by screwing on or slipping on and twisting, onto a stationary connection, for instance of a motor vehicle radiator, a compensation vessel in cooling or heating systems, or the like.
Such closure covers are known from German patent DE 44 22 292 A1. They are used for instance in motor vehicle cooling systems, either directly as a radiator cap or as a closure for the compensation vessel. The closure cover can either be screwed on by means of a thread or slipped on and twisted by means of a bayonet element. In motor vehicle cooling systems, there is a problem with respect to the closure cover, which is that as a rule, because of the high temperature in the cooling system, the pressure is also high.
Even if at the moment the engine is turned off the temperature in the cooling system is not overly high, still an increase in temperature and thus pressure can occur in the cooling system after engine shutoff from a certain residual heating effect. If the user then immediately removes the closure cover of the cooling system, he runs an acute risk of being burned. This risk exists particularly in screw-type closure covers, because on unscrewing the closure cover the user is not made to slow down the unscrewing in the final phase or even better to interrupt it in order to make a pressure equalization with the ambient air and above all to wait. When a closure cover is screwed onto the cooling system, it is true that a venting connection to the outside is opened, but venting for pressure equalization cannot happen as fast as the user can possibly unscrew the closure cover completely. The same is correspondingly true for the use of a cover with a bayonet closure.
It is an object of the present invention to provide a novel structural form, with which coupling in a manner fixed against rotation at normal temperature and uncoupling at excess temperature can be reached equally reliably as with the known closure cover, and which allows a novel design of the components that cooperate for coupling and uncoupling.
To attain this object, in a closure cover of the type defined at the outset, the closure cover, in the state in which it is put on the stationary connection, can be secured against removal, preferably by unscrewing or untwisting, by means of a temperature-dependent control element, and the temperature-dependent control element a coupling part, is movable substantially approximately radially between a coupling position and a release position.
By means of the provisions of the present invention, a closure cover is created which, whenever a critical high temperature still prevails in the cooling system (or in the heating system) it cannot be removed. Injuries from high temperature and the resultant overpressure in the stationary connection when the closure cover is opened are thus prevented in every case. The temperature-dependent control element is accommodated in a space-saving way together with the coupling element.
In accordance with one exemplary embodiment, it is possible for the temperature-dependent element to be provided between the cap and the valve, and the cap and the connection, so that the cap is locked in a manner fixed against relative rotation relative to the stationary connection.
A preferred embodiment of the present invention is realized in accordance with the fact that the engagement part is held rotatably relative to the cap, and that with the said of the temperature-dependent control element, a coupling, in a manner fixed against relative rotation, between the cap and the engagement part, is attainable at normal temperature, and a decoupling between them is attainable at excess temperature. As a result, in the event of an overtemperature, the cap turns uselessly relative to the engagement part, so that it is not possible, even by force, to release the closure cover from the stationary connection.
Japanese patent, JP 62159721 discloses a twist-off prevention means with radially movable components. This closure cover, however, is not of the same generic type as that of the present invention since it has no engagement part that is rotatable relative to the cap. The same is true of German patent, DE 38 28 462 A1.
Further details of the present invention can be learned from the ensuing description, in which the present invention is described and explained in further detail in terms of the exemplary embodiments shown in the drawing.